JPH0487868A - Brake control device - Google Patents

Abstract

PURPOSE:To obtain excellent pedal feeling at a brake operating time when a pressure control means functions by providing a changing over valve and a restricting element in parallel on the way of a brake fluid pressure passage from a master cylinder to a pressure control means for controlling brake fluid pressure toward each wheel cylinder. CONSTITUTION:An on-off electromagnetic valve 6 (changing over valve) is provided between a master cylinder pressure oil passage 4 from a master cylinder 2 to generate brake fluid pressure by the pressing operation of a brake pedal 1 to a wheel cylinder 3 provided on each wheel to generate braking force on a wheel by the brake fluid pressure and a wheel cylinder pressure oil passage 5. Moreover, an orifice 24 (restricting element) is provided on a bypass oil passage 23 bypassing the on-off electromagnetic valve 6, and even if the valve 6 is closed, the master cylinder 2 and the wheel cylinder 3 are made to mutually communicate through the restricting element 24 to make pressure fluctuation on the side of the master cylinder 2 smoother than that on the side of the wheel cylinder 3 for producing excellent pedal feeling without a plate pressing feeling and a kickback.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a brake control device that controls brake fluid pressure independently for each wheel.

(Prior art) Conventionally, as a brake control device, for example,
Devices described in Japanese Patent Application Laid-Open No. 149542-149542 and Japanese Patent Application Laid-open No. 149543-1988 are known.

The former publication states that an on/off valve is provided between the master cylinder and the wheel cylinder, a movable piston is arranged downstream of the on/off valve, the output chamber of the movable piston communicates with the wheel cylinder, and the input chamber of the movable piston is connected to a pressure control valve. The device is shown connected to a second hydraulic power source via a second hydraulic pressure source.

In the latter publication, a pressure modulator is provided between the master cylinder and the wheel cylinder, and this pressure modulator receives control pressure chamber and wheel cylinder pressure from a pressure control valve having a master cylinder pressure chamber and a second hydraulic pressure source. A device is shown in which a chamber is formed.

(Problem to be Solved by the Invention) However, in such conventional brake control devices, when the pressure control valve operates, the master cylinder and the wheel cylinder are either isolated or directly connected. Because of this configuration, there are problems with the pedal feel being flat and the kick pack being large.

The present invention has been made in view of the above-mentioned problems, and is a brake control device that independently controls brake fluid pressure for each wheel. The challenge is to obtain a good pedal feel.

(Means for Solving the Problems) In order to solve the above problems, in the brake control device of the present invention, the brake fluid pressure path from the master cylinder to the pressure control means for controlling the brake fluid pressure to each wheel cylinder is A switching valve and a throttling element are provided in parallel.

That is, a master cylinder that generates brake fluid pressure by operating the brake operating means, and a master cylinder provided for each wheel,
A wheel cylinder that generates braking force on the wheels by brake fluid pressure, a pressure control means that balances the brake fluid pressure to each of the wheel cylinders, and a brake fluid pressure path that extends from the master cylinder to the pressure control means, and that A switching valve and a throttle element are provided in parallel.

(Function) When the wheel cylinder pressure is desired to be increased or decreased from the master cylinder pressure during brake operation, the pressure control means is activated to open the wheel cylinder pressure to a higher or lower pressure than the master cylinder pressure.

Even if the switching valve is closed when this pressure control means is activated, the master cylinder and wheel cylinder communicate through the throttle element, so the pressure change on the master cylinder side is smoother than the pressure change on the wheel cylinder side. This results in a good pedal feel with no board feel or kick pack.

(Example) Embodiments of the present invention will be described below based on the drawings.

First, the configuration will be explained.

FIG. 1 is an overall diagram showing a first embodiment of the brake control device, which is applied to ideal distribution control of front and rear, left and right braking forces, and the like.

The brake control device of the first embodiment includes a master cylinder 2 that generates brake fluid pressure by depressing a brake pedal 1 (brake operating means), and a master cylinder 2 that is provided for each wheel (not shown), and is provided for each wheel (not shown). a wheel cylinder 3 that generates braking force; an on/off solenoid valve 6 (switching valve) provided between the master cylinder pressure oil passage 4 and the wheel cylinder pressure oil passage 5 from the master cylinder 2 to the wheel cylinder 3; It includes a plunger piston 7 disposed midway in the wheel cylinder pressure oil passage 5 at a position downstream from the on-off solenoid valve 6, and an orifice 24 (throttling element) provided in a bypass oil passage 23 that bypasses the on-off solenoid valve 6. There is.

The first oil chamber 7a of the plunger piston 7 communicates with the wheel cylinder 3, and the second oil chamber 7b communicates with the control pressure oil passage 8. Pressure control valve9. The accumulator pressure oil passage 10 communicates with a hydraulic pump 11 and an accumulator 12, which generate hydraulic pressure regardless of brake operation, and these members constitute a pressure control means.

The operation of the on-off solenoid valve 6 and the pressure control valve 9 is controlled by a flake control unit 13.

Although not shown, the on/off solenoid valve 6° plunger piston 7, pressure control valve 9, and orifice 23 are
One is provided for each section of the wheel.

The plunger piston 7 includes a piston 7C having a smaller diameter on the first oil chamber 7a side and a larger diameter on the second oil chamber 7b side;
It has centering springs 7d and 7e that urge the different diameter piston 7c from both sides.

A check valve 14 is provided in an oil passage connecting the hydraulic pump 11 and the accumulator 12 to allow flow only from the hydraulic pump 11 to the accumulator 12.

Brake control unit 13 (steering angle sensor 15. yaw rate sensor 16. lateral acceleration sensor 179 longitudinal acceleration sensor 18. vehicle speed sensor 19. wheel speed sensor 20. master cylinder pressure sensor 21. wheel cylinder pressure sensor 22) The target brake fluid pressure is determined based on the preset target brake fluid pressure characteristics and the braking state and driving state obtained from the sensor signal, and the target brake fluid pressure and the actual wheel cylinder are A control command is output to each solenoid 6a, 9a of the on/off solenoid valve 6 and the pressure control valve 9 so as to eliminate the deviation from the pressure.

Next, the effect will be explained.

(a) During normal braking During normal braking, the brake control unit 13
A valve opening command is outputted to the on-off solenoid valve 6, and a valve operation command to maintain the reference control pressure is outputted to the pressure control valve 9.

Therefore, brake fluid pressure is generated in the master cylinder 2 by the brake operation on the brake pedal 1, and this master cylinder pressure is sent to the wheel cylinder 3 via the master cylinder pressure oil path 4 and the wheel cylinder pressure oil path 5, and is sent to the wheel cylinder 3 through the master cylinder pressure oil path 4 and the wheel cylinder pressure oil path 5. Braking force is applied to each wheel by the wheel cylinder pressure, which is the same as the cylinder pressure (Flower in Figure 2).

(b) During pressure increase The pressure increase mode that increases the wheel cylinder pressure from the master cylinder pressure during brake operation has the following three pressure increase modes depending on the operation command from the brake control unit 13 to the on/off solenoid valve 6. There is.

There is a pressure increase mode in which the on-off solenoid valve 6 is opened (flow ll-1 in Figure 2), a pressure increase mode in which the on-off solenoid valve 6 is controlled on and off (flow 1-2 in Figure 2), and an on-off mode. There is a pressure increase step by closing the solenoid valve 6 (Flow ①-3 in Fig. 2).

In the pressure increase mode with the on/off solenoid valve 6 open, the on/off solenoid valve 6 is connected to the brake control unit 13.
An opening command is output to the pressure control valve 9, and a valve operation command is output to the pressure control valve 9 to set the pressure higher than the reference control pressure.

Therefore, brake fluid pressure is generated in the master cylinder 2 by a brake operation on the brake pedal 1. On the other hand, due to the high control pressure applied to the second oil chamber 7b of the plunger piston 7, the volume of the first oil chamber 7a of the plunger piston 7 is reduced.

As a result, the master cylinder pressure is increased by reducing the volume of the first oil chamber 7a of the plunger piston 7, and this increased wheel cylinder pressure provides braking force to each wheel. Moreover, since the on/off solenoid valve 6 is open,
As shown in flow ①-1 of FIG. 2, the master cylinder pressure is also applied to the wheel cylinder 2, and the pedal depression force is increased in accordance with the pressure increase width.

When the on-off solenoid valve 6 is in the pressure increase mode with on-off control, an on-off command is output from the brake control unit 13 to the on-off solenoid valve 6, and a valve operation command is output to the pressure control valve 9 to make the pressure higher than the reference control pressure. be done.

Therefore, as shown in flow 11-2 of FIG. 2, the wheel cylinder pressure characteristic, which is the C-point characteristic, is the same as in the pressure increasing mode with the on-off solenoid valve 6 open, but the master pressure characteristic, which is the B-point characteristic The cylinder pressure characteristics tend to exhibit stepwise pressure changes due to opening/closing control by the on/off solenoid valve 6.

However, when the on-off solenoid valve 6 is closed, the orifice 24
As a result, the step-like pressure change characteristic becomes smoother due to the slight increase in pressure, and in addition, the further pressure change in the master cylinder 2 is attenuated and the pedal force retention, which is the A point characteristic, becomes smooth. This will result in a good pedal feel.

Note that the pattern of pressure change in the master cylinder pressure can be arbitrarily changed by the time distribution of the on time and off time for the on/off solenoid valve 6.

In the pressure increase mode in which changes in pedal depression force are suppressed, a closing command is output from the brake control unit 13 to the on/off solenoid valve 6, and a valve operation command is output to the pressure control valve 9 to set the pressure higher than the reference control pressure.

Therefore, as shown in flow 11-3 of FIG. 2, the wheel cylinder pressure characteristic, which is the C point characteristic, is the same as in the pressure increase mode with the on/off solenoid valve 6 open, but the master pressure characteristic, which is the B point characteristic The cylinder pressure characteristics show a smooth pressure rise characteristic because only a small amount of brake fluid is allowed to flow through the orifice 24 even when the on-off solenoid valve 6 is closed, and the pedal pressure changes at point A. It also becomes smoother and allows you to get a good pedal feel.

(c) During pressure reduction As a pressure reduction mode in which the wheel cylinder pressure is reduced from the master cylinder pressure during brake operation, there are the following three pressure reduction modes depending on the mode of the operation command from the brake control unit 13 to the on/off solenoid valve 6.

A pressure reduction mode by opening the on-off solenoid valve 6 (flow m-1 in Figure 2), a pressure reduction mode by controlling the on-off solenoid valve 6 on and off (flow -2 in Figure 2), and a pressure reduction mode by opening the on-off solenoid valve 6 (flow m-2 in Figure 2). There is a decompression mode in which 6 is closed (flow ①-3 in Figure 2).

When the on-off solenoid valve 6 is opened and the pressure is reduced, the on-off solenoid valve 6 is connected to the brake control unit 13.
An opening command is output to the pressure control valve 9, and a valve operation command to set the pressure to be lower than the reference control pressure is output to the pressure control valve 9.

Therefore, brake fluid pressure is generated in the master cylinder 2 by a brake operation on the brake pedal 1. On the other hand, due to the low control pressure applied to the second oil chamber 7b of the plunger piston 7, the volume of the first oil chamber 7a of the plunger piston 7 is expanded.

As a result, the master cylinder pressure is reduced by expanding the volume of the first oil chamber 7 of the plunger piston 7, and this reduced wheel cylinder pressure provides braking force to each wheel. Moreover, since the on/off solenoid valve 6 is open,
As shown in flow ① of FIG. 2, the master cylinder pressure is also applied to the wheel cylinder 2, and the pedal depression force is reduced in accordance with the pressure reduction range.

When the on-off solenoid valve 6 is controlled on and off to perform pressure reducing mode, an on-off command is output from the brake control unit 13 to the on-off solenoid valve 6, and a valve operation command is output to the pressure control valve 9 to set the pressure lower than the reference control pressure. Ru.

Therefore, as shown in flow m-2 in FIG. 2, the wheel cylinder pressure characteristic, which is the C point characteristic, is the same as in the pressure reduction mode with the on-off solenoid valve 6 open, but the master cylinder pressure characteristic, which is the B point characteristic, is the same as in the pressure reduction mode with the on-off solenoid valve 6 open. The pressure characteristics tend to show stepwise pressure changes due to opening/closing control by the on/off solenoid valve 6.

However, when the on-off solenoid valve 6 is closed, the orifice 24
As a result, the step-like pressure change characteristic becomes smooth as a small pressure drop is observed, and in addition, further pressure change or attenuation is alleviated in the master cylinder 2, and the pedal depression force characteristic, which is the A point characteristic, changes smoothly. This results in a good pedal feel.

In the pressure reduction mode with the on-off solenoid valve 6 closed, the on-off solenoid valve 6 is connected to the brake control unit 13.
A close command is output to the pressure control valve 9, and a valve operation command to set the pressure to be lower than the reference control pressure is output to the pressure control valve 9.

Therefore, as shown in flow 1ll-3 in FIG. 2, the wheel cylinder pressure characteristic, which is the C point characteristic, is
The master cylinder pressure characteristics, which are the same as in the pressure reduction mode with the valve open, or the B point characteristics, are such that even if the on-off solenoid valve 6 is closed, a small flow of brake fluid is allowed through the orifice 24. This shows a smooth pressure rise characteristic, and the change in pedal force at point A is also smooth, making it possible to obtain a good pedal feel.

(d) When the brake is not operated When you want to apply braking force to each wheel when the brake is not operated, the on/off solenoid valve 6 is sent from the brake control unit 13.
A command to close the valve is output to the pressure control valve 9, and then a predetermined valve operation command is output to the pressure control valve 9.

Therefore, when the on-off solenoid valve 6 is closed, hydraulic oil is sealed in the wheel cylinder pressure oil passage 5 from the on-off solenoid valve 6 to the wheel cylinder 3, and is added to the second oil chamber 7b of the plunger piston 7. The volume of the first oil chamber 7a of the plunger piston 7 is reduced depending on the magnitude of the control pressure.

As a result, braking force is applied to each wheel by the wheel cylinder pressure that corresponds to the increase or decrease in the volume of the first oil chamber 7a of the plunger piston 7.

That is, a constant braking force can be applied to the wheels by applying control pressure to the plunger piston 7, or a desired varying braking force can be applied to the wheels by monitoring the wheel cylinder pressure with the sensor 22 and feedback control. It can also be added to.

Next, an example of braking force control during brake operation will be described.

- Front and rear braking force ideal distribution control The front and rear wheel cylinders are controlled based on the vehicle's longitudinal acceleration state (or front and rear wheel load state) detected by longitudinal acceleration x 6 etc. and the preset front and rear ideal braking force distribution characteristics. Controls the pressure to increase or decrease relative to the master cylinder pressure.

As a result, an ideal distribution of front and rear braking force without early locking of the rear wheels can be achieved.

・Left and right braking force ideal distribution control lateral acceleration Y6. Masters the wheel cylinder pressure of the left and right wheels based on the vehicle turning state detected by the yaw rate φ, steering angle θ, vehicle speed V (or left and right wheel load state), etc., and the preset ideal right and left braking force distribution characteristics. Controls increase/decrease in cylinder pressure.

As a result, an ideal distribution of braking force between the left and right sides without premature locking of one wheel can be achieved.

・Anti-skid control The slip rate of each wheel is calculated from the vehicle body speed based on the integral value of longitudinal acceleration x 6 and the wheel speed V, and the wheel cylinder pressure is feedback-controlled so that this slip rate becomes the ideal value.

This prevents the axle from locking during braking on low μ roads or during sudden braking, resulting in shortened braking distance and improved braking stability.

Next, an example of braking force control during non-braking operation will be described.

・Steering characteristic control lateral acceleration Y6. The wheel cylinder pressure is controlled to increase or decrease so that the actual steering characteristic state during turning, which is detected by the yaw rate ψ, steering angle θ, vehicle speed V (or left and right wheel load state), etc. becomes neutral steering according to the driver's steering intention. .

This prevents strong understeer or strong oversteer characteristics when turning.

・Straight-line maintenance control If disturbances such as road surface irregularities or crosswinds cause a change in the vehicle's lateral acceleration or yaw rate, this will be detected and the braking force will be adjusted to correct it immediately.

This allows the vehicle to maintain straight travel without being affected by disturbances.

Yaw rate control The deviation between the yaw rate φ obtained from the yaw rate sensor 16 and the target yaw rate obtained from the vehicle speed V and steering angle e is determined, and the braking force is controlled to adjust the pressure so as to eliminate this deviation.

This makes it possible to obtain optimal yaw rate characteristics when traveling straight or when turning.

As explained above, in the flexible control device of the first embodiment, the effects listed below can be obtained.

■ An on-off solenoid valve 6 between the master cylinder pressure oil passage 4 and the wheel cylinder pressure oil passage 5 provided with pressure control means.
and the orifice 24 are provided in parallel, so when the on-off solenoid valve 6 is closed when the plunger piston 7 is activated, the pressure in the three wheel cylinders is transmitted to the master cylinder 2 via the orifice 24. , it is possible to obtain a good pedal filling without a board feeling or kick pack when operating the brake.

■ The switching valve is an on/off solenoid valve 6 that is controlled to open and close by external commands, which eliminates the discomfort of brake operation when controlling the increase/decrease of wheel cylinder pressure and expands the width of hydraulic control of wheel cylinder pressure. As mentioned above, it is possible to provide an effective device for various braking force control systems.

In other words, at least the brake pedal pressure does not have an inverse relationship where the wheel cylinder pressure decreases when the pressure increases and increases when the pressure decreases, and if the on/off solenoid valve 6 is controlled to turn on/off, the pedal feel will not feel strange. You will get a ring.

Additionally, when the pressure is reduced during brake operation, the wheel cylinder pressure can be reduced to a pressure level lower than the master cylinder pressure, expanding the hydraulic control range of the wheel cylinder pressure and making it possible to impose control limits on the braking force control system. do not have.

Next, a second example will be described.

FIG. 3 is a diagram showing a brake control device according to a second embodiment. In the first embodiment, an example of an on-off solenoid valve 6 which is externally controlled to open and close as a switching valve is shown, but in this second embodiment, a switching valve is used. This is an example in which a hydraulically operated on-off valve 25 that mechanically switches from a valve open state to a valve closed state using the oil pressure of a control pressure oil passage 8 as a pilot pressure is applied as a valve.

Note that the other configurations are the same as those in the first embodiment, so corresponding configurations are denoted by the same reference numerals in the drawings and description thereof will be omitted.

Effectively, it is possible to obtain the effect of improving the pedal feel described in section (2) in the first embodiment.

Although the embodiment has been described above based on the drawings, the specific configuration is not limited to this embodiment.

For example, as the pressure control valve, a proportional valve or a duty valve may be used.

Further, the hydraulic pump 11 may be used in common with a hydraulic pump in another control system (for example, a power steering system, a suspension control system, etc.) mounted on the vehicle.

(Effects of the Invention) As explained above, in the present invention, in the brake control device that controls the brake fluid pressure on each brake cylinder,
A switching valve and a throttling element are provided in parallel in the middle of the brake fluid pressure path from the master cylinder to the pressure control means that controls the brake fluid pressure to each wheel cylinder, so when the brake is operated when the pressure control means is activated, the plate is depressed. The effect is that it is possible to obtain a good pedal feeling without any kickback or kickback.

[Brief explanation of the drawing]

Fig. 1 is an overall diagram showing the brake control device according to the first embodiment of the present invention, and Fig. 2 shows each mode of normal control, pressure increase control, and pressure reduction control during brake operation using the brake control device according to the first embodiment. FIG. 3 is an overall view showing a brake control device according to a second embodiment of the present invention. 1...Flake pedal (brake operation means) 2...-
Master cylinder 3 - Wheel cylinder 4... Master cylinder pressure oil path (brake fluid pressure path) 5... Wheel cylinder pressure oil path (brake fluid pressure path) 6... On/off solenoid valve (switching valve) 7. -Plunger piston 7a...First oil chamber 7b...Second oil chamber 8...Control pressure oil passage 9...Pressure control valve 10...Accumulator pressure oil passage 11...-Hydraulic pump 12 ...Accumulator 13...Brake control unit 24...-
Orifice (aperture element)

Claims (1)

[Scope of Claims] 1) A master cylinder that generates brake fluid pressure by operating a brake operating means, a wheel cylinder that is provided for each wheel and that generates braking force on the wheel using brake fluid pressure, and each of the wheel cylinders. A pressure control means for controlling brake fluid pressure to the pressure control means; and a switching valve and a throttle element provided in parallel with each other in the middle of a brake fluid pressure path from the master cylinder to the pressure control means. brake control device.